1. Field of the invention
The present invention relates to a steering system in a wheeled vehicle, and more particularly to a steering system in a wheeled vehicle the front-wheel steering linkage of which is interconnected to a rear-wheel steering linkage to selectively steer the rear road wheels in response to steering operation of the front road wheels.
2. Discussion of the background
Such a four-wheel steering system as described above has been proposed in Early Publications for Japanese Patent Nos. 59-26363, 59-26364 and 59-26365, which steering system comprises a front-wheel steering linkage arranged to be operated by a steering wheel, a rear-wheel steering linkage including a lateral control shaft operatively connected at the opposite ends thereof with a pair of rear steerable road wheels, a rotary shaft extending longitudinally in a fore-and-aft direction of the vehicle and operatively connected at the front end thereof with the front-wheel steering linkage, and a rear-wheel steering mechanism operatively connected to the rear end of the rotary shaft to effect axial displacement of the lateral control shaft in response to rotary motion of the rotary shaft. For the purpose of controlling the steering angle ratio and direction of the rear road wheels relative to the front road wheels, the rear-wheel steering mechanism comprises an input shaft arranged to be rotated by the rotary shaft, an output shaft swingably connected at one end thereof with the input shaft by means of a universal joint and integrally connected at the other end thereof with the lateral control shaft of the rear-wheel steering linkage, and an actuator assembly arranged to incline the output shaft with respect to the input shaft. In this arrangement, the actuator assembly is activated to adjust the inclined angle of the output shaft for controlling the steering angle ratio and direction of the rear road wheels relative to the front road wheels. However, the adjustment of the inclined angle of the output shaft causes axial displacement of the lateral control shaft in a condition where the rotary shaft is stopping. This results in change of the alignment of the rear road wheels.